By Marty Graham
SAN DIEGO, Jan 28 (Reuters) - California sea lions - mainly pups - are turning up stranded and starved on Southern California beaches in record numbers this year, leaving experts worried that this winter may be the worst season ever documented for the marine mammals.
The precise cause is not clear, but scientists believe the sea lions are suffering from a scarcity of natural prey that forces nursing mothers to venture farther out to sea for food, leaving their young behind for longer periods of time.
Experts theorize that this winter's mild El Nino effect, which alters ocean currents and temperatures, may be compounding the shortage of fish that sea lions rely on for food, said Keith Matassa, executive director of the nonprofit Pacific Marine Mammal Center in Laguna Beach.
That group's pup rescues for the month are already running 20 percent above the same period in 2013, when the National Marine Fisheries Service declared an "unusual mortality event" in which five times the normal number of pups were in need of assistance, Matassa said.
While the majority of the stranded animals this year are less than 1 year old, emaciated adults are also turning up, Matassa said.
Officials at SeaWorld in San Diego and the Marine Mammal Care Center in San Pedro also reported a dramatic increase in the number of sea lions they are rescuing and rehabilitating.
"Our numbers are twice what they were in 2013," said David Bard, operations director of the San Pedro center. "In 2013, we saw an unprecedented number of rescues, it was a record then."
Bard's facility has taken in more than 70 rescued sea lion pups since December, he said, while the Laguna Beach center has taken in 29. SeaWorld has rescued 62 sea lions - juveniles and adults - since Jan. 1, with 15 starved pups coming in during the past three days, rescue team coordinator Jody Westberg said.
It takes six to eight weeks for the pinnipeds to regain enough strength to be returned to the wild.
Inside an enclosure at SeaWorld, about a dozen sleek pups barked and groomed each other on Wednesday, oblivious to the egret that had come to take their food.
"When they came in, they couldn't raise their heads, so to see them start grooming and barking, that means they're feeling much better, much more themselves," SeaWorld veterinarian Dr. Hendrik Rollens said. "They are ready to go back to the wild." (Editing by Steve Gorman; Editing by Sandra Maler)